Variable condenser



Dec. 1 1925 LSSTSMO A. RUSSELL VARIABLE CONDENSER Filed Feb. 3., 1925 Isubject of the To all whom, t may concern:

Patented Dec." 1925.

UNITED STATES l 1,563,440 PATENT oFFlcE.

ARTHUR RUSSELL, OF BALTIMORE. MARYLAND, ASSIGNOR TO THE RUSSELL RADIOICOBPORATION, OFVBALTIMORE. LIARYLAND. A CORPORATION OIE'` MARYLAND,

VARIABLE ooNDENsER.

Application filed February 3, 1925. SeriatNo. 6,501.

Be it known that I, ARTHUR RUSSELL, a

Kino' of Great Britain. residing in ,the city of altimore,` State ofMaryland. U. S. A., have invented certain new and useful ImprovementsinV Variable Con'- densers, Vof whichthe following is a specification. l5

' One of the importantdiiculties incident to the operation or" radio`receiving sets. is'

that incident to tuning in on the various stationswhich in the mainconsists in adjusting the condenserv to the particular wave length ofthe sending station from which it is desired to receive.` 'The'commonest type of variable condenser consists of a stator composed of aseries 'of stationary spaced metal plates and a rotor consisting of asecond series of rotatable spaced metal plates which intermesh with theplates of the rotor, Aand are spaced therefrom by a suitableair gap. Thestator plates are insulated from the rotor plates' and all of the platesarel in planes at rightvangles to the axis of rotation.

In the present well-known type of variable condenser thus described, thedesiredadjustment as to wave length is obtained by moving thelrotorabout its axis` relatively to the stator so as to change the rela-v tionof the plates, changing the cross-section oi the air gap between theplates ofthe stator` and the plates of the rotor without changing thespacing, ordinaril)T termed the width,y of the air gap.

The dial by V,which the rotor is turned and by which its position isindicated, is ordinarily connected directly tofthe axis ot the rotor,and the adjustment requisite to satisfactory results is Vso tine as toxmake it exceedingly diliicultvto obtain in this way, wherein is involvedthe necessity for a high degree of skill on the part of the operator.

- A further difficulty is that the variation or band ofwave lengths.obtained by the ad'- `manufacturers to make and the dealers to carry instock condensers of various capacities having different numbersofiplates andv further making vit necessary for the radio enthusiast whorebuilds his set, tochange and possibly discard his condenser withcorresponding frequency. and expense.

'The presentinvention eliminates andovercomes to a large degree thedefects and difficulties thus presented, giving a much liner adjustmentto wave lengths with a less exercise of skill on the part of theoperator. at the Sametime providing for adjustment or timing of theapparatus to a -much greater variation,l or as. it is stated inv theterminology of the art, to a much broader band of wavelengths than anyotl the condensers now in use.

Also the apparatus permits of an easy and quick adjustment as to ritscapacity, so that for the ordinary commercial apparatus it is onlynecessary to manufacture a condenser of a single capacity, and it isonly necessary for the dealer in such commercial apparatus to carry asingle condenser or` condensers of a single capacity in stock, and theradio enthusiast oramateur who rebuilds his set may change the capacityof his condenser at will to conform to the corresponding change in hisset. The improved condenser .may be produced economically atdecreasedexpense com'pared to the present type, and it. is so constructed that itis less apt to get out of order than are the' commercial types ofcondenser now in use, and it maytherefore be described as offlonger lifeor longer v average life. l

lcoi-responding points of any circle drawn about the same axis as acentre. Preferably the plates are spirally Woundor coiled aftcrthemanner of a clock spring. the width of the plates being parallel. tothe axis, anfl one plate isenclosed Within the other. As

shown, the rotor is enclosed` within the stator,y i. e., has each turn,loop .or coil placed between two corresponding turns or coils ot thestator, so that the two plates or bands are substantially concentric andparallel and rotatable through anarc, one relativelyto the other.

. the lparallel relation .and gives a change of spacing of the platesand a wide change of capacity of the condenser. In the form shown thestator plate `orspiral is secured to the panel and the rotor is mountedon a. shaft for angular adjustment relatively to the stator about theaxis ofthe stator and its own axis whiclrare preferably identical.

For the purposes of this adjustment as to capacity, I have provided adial or similar' member connected to the vrotor by which it may berotated and its position relatively to the panel and the stator suitablyindicated;

For the purposes of adjustment of the apparatus to the Wave lengths ofthe various the capacity adjustment.

stations from which it is desired to receive, one of the plates is movedrelatively to the other in a direction parallel to the axis in anysuitable manner. Preferably the rotor ismounted to move along the shaftinto and out of the stator, changing the cross-section of the air gap.Inthe form shown the adjustment as to wave lengths is obtained by meansof a screw threaded, akially placed rod or pin extending through theshaft on which the rotor is mounted, by which threaded pin the rotor ismoved in the direction of its axis relatively to the stator `by turninga suitable nut or knob engaging the thread, giving an exceedingly vwiderange of adjustment, making it possible to change the cross-sectionofthe air gap from zero -to the maximum available when the rotor isalmost or completely enclosed Within the stator. The rotor is duringthis operation held against rotation by means of a suitable key orequivalent device which connects it to the shaftwith which it is turnedduring The axial adjustment provides for variation of thecross-sectional area, of the air gap land by means of the screw andknob,a much finer adjustment as to this element,

which tunes the set to theI wavelength of' thesending set, may beobtained than with the type of condenser in which the rotor plates aremerely swung by means of and with the dial, and at the same time thisapparatus obtains or provides for an adjustment to a greater variationof wave length 1 or broader band of wave lengths than can be obtained byany 'other known instru- ,1t-@11t- 110" Provided fer this puriose.

In the accompanying drawings I have illustrated 'a variable condenserembodying the features of my invention in the pre,- JEerred form. y i

In the drawings- Figure l is a longitudinal section on the plane of theaxis of the condenser plates showing the complete condenser assembled.

Maaate rotation to provide for variation of capacity. The adjustment isfor maximum capacity. f

Figure l is an elevation looking at the front of the panel showing thedial, knob, etc., at minimum capacity. t

Figure .3 is a section on the line 5,5 of Figure l through the hollowshaft, screwadjusting pin and hub, showing the stop'` which limits therotation of the hollow shaft and therefore the angle through which theplates may be rotated to adjust for capacity. 3

Referring to the drawings numerals, each of which is used to indicatethe same or similar parts in the different figures, the variablecondenser as shown comprises concentric and substantially'parallel,condenser platesyone enclosed Within the otherand indicated byreference characters l and '2, the plates beingshown'each in the form ofa coiled or spiral band having theiriwidth parallel to the axis of thespiral and each having its respective tiirns equally spaced andMsubstantially parallel, the pitch being uniform throughout, and asis-usual-in such apparatus, the stator l is insulated from the rotor 2.

or more properly to the condenser base 4 by means of suitable clips onbrackets 5 which may be soldered to the stator plate and bvy screws 6engaging the brackets 2.v

The base t is' in turn securedto the anel. Both the base 4 and the panel3 are o hard rubber or other suitable insulating material. The' stat-orpla-te l is preferably spaced .away from the base, as indicated at 7.The plates manner as' at 6 and 6.

The loopsj or turns of the'stator plate l are spaced apart and securedinthe desired relation, and the en'tire stator coil structure. M is maderigid by radially placed studs or y K Il The stator'l'jl is sejcured tothe panel 3,

110,l mayT` be connected to the circuit in the usual plate between therespective loops or turnsy of the stator plate, andthe loops or turns ofthe stator plate 2 are similarly bra-ced by radial studs 15 connectingthem at their outer edges. i. e., the edges remote from the panel, seeFig. l, so that these studs or strutsL 13 interfere as little aspossible with the entrance of the rotor plate V2.to the full width ofthe plate between the turns or coils` 16 secured at its radial endswithin the insecured a pin 19. The

ner turn or loop 17 of the rotor. This support 16 carries a central hub18Vto which is pin 19 is concentric and aligned with the axis of bothplates, being as aforesaid secured at one end to thecentre of the rotorplate 2 and extending forwardly through shaft 22 which is made hollow toreceive it, through the stator plate 1, through the panel and projectingbeyond the panel for a suiiicient length to` provide' for adjustmentofthe plate 2 in the direction of its aXi/s for a large proportionof'the Width of the plates. The forward end of the pin in front of theplates is threaded at 2O to co-operate with a nut or knob 21,

suitably apertured and threaded to co-operate with the thread on thepin. The pin 19 is mounted to slide in the hollow shaft 22` which isconcentric and aligned therewith andmounted in a bearing formed in aboss 24 which as shown -is formed integral with a plate 25 secured inany suitable manner to Ithe condenser base or base plate 4 or to thepanel 3.

The shaft 22 referred to hereinafter as the rotor shaft may be actuatedand controlled, and its position determined by a dial l 26 suitablyapertured at its centre to admit the shaft and secured thereto in anysuitable manner as by means of a set-screw 2 7. This dial may besuitablyV graduated at 28, see Fig. 4, and the panel may be providedwith a pointer 29 to co-operate with the graduations. The resistance orfriction of the panel is adjusted by means of a screw 40 seated in thedial and bearing on the panel.

The rotor shaft 22 may be connected to the rotor 2 in any suitablemanner to cause the rotor to turn withthe shaft 22 and to permit therotor to slide freely in the direction of the axis of the shaft. In theform of the invention shown this keying arrangement consists of a pin 30parallel to the `shaft 22 and 'the pin 19 and spaced well' position therotor shaft 22 by contact of the fiange with the end of the boss 24thehollow rotor shaft 22 being thrust forwardly, maintaining the ange.33 incontact with the end of the boss by means of a coilspring 34 Which iscoiled about the rod 19 at the A rear, bearing at one end against theforward side of the spider plate 16 and at the other Aend against theflange This spring also tends to thrust the rotor plate rearwardly, i.e., to the right in-Figure 1, causing it to more to the right out of thestator as the vrod 19 is released by unscrewing the knob or Y nut 21 andpermitting it to be drawn tothe left, causing it to enter the stator asvtlie vnut or knob `is turnedwup on the rod 19,

giving the desired adjustment' of' the cross Y section of the air ygapto provide for interpreting different wave lengthsx The rotation orangular displacement of t-he rotor 2 from minimum capacity positionrelatively to the stator 1, is'definitely limited "by means of aradially projecting stop 36, see Fig. 5, on the rotor shaft 22whichrides in an open slot 37 attheend Opf-boss 21.

The minimum capacity position of the rotor, Fig. 2, is determined by thecontact of the stop 36 with the edge 39 of the slot 37, and the maximumposition, Fig. 3, by contact with the opposite edge 38. The spacing ofthe plates is thus changed and the parallel relation maintained Aby andon account of the-concentric location of the plates and the uniformpitch- These elements may be varied to some degree without complete lossof the function. Y I

In the'operation of the condenser, to adjust for. capacity to adapt thecondenser to any particular receiving set, the rotor4 2 is turned 'fromthe position shown in Fig. 2

tothe left relatively to the stator l'toward the position inl Fig. 3toreduce the spacing of the plates," causing the loops or turns of therotor by the variation inradius ofthe stator and rotor, to approach theloops of t-he stator, thus changing the width of the which one or moreplates of one element are j adjusted toward and' from the adjacentplates of the-other element, Vthe rotation of the lpresent type ofcondenser whereby the spacing of the entire rotor relatively to thestator Vis changed by a single adjustment by rotating one elementrelatively to the other about the common centre, is regarded as animportant feature ofthe invention, producing a wide scope of adjustmentas to 'capacity without lcomplication of structure and by a very4 simpleoperation. e

To tune the receiving set to the wave lengths of any transmitting setfrom which 1t is desired to. receive, the cross-sectionl lain of the airgap is changed. n exceedingly fine adjustment is obtained by rotatingthe nut or knob 21 either taking up or letting out the threaded pin 19.moving the rotor relatively to the stator in the direction of the commonaxis, changing the position of the rotor 2 as to the extent to which itis enclosed Withinv the stator 1.', and while a very minute adjustmentmay be easily obtained in this vvayfthereis on account of the widepossible variation ot' position of t-he rotor 2 relatively to the stator1, a wide range of adjustment, and the apparatus may be adjusted withextreme accuracjv and Without the exercise of slrill requisite with thecondenser-s now` in use, to and through a broad band of `wave lengths,than can be Letters Patent is 1. A variable condenser having a rotor anda stator each comprising a plate Wound in a Spiral about the mutualcommon axis7 the two plates being adapted to intermesh with and beingspaced troni each other, and means to change the relative spacingbetween the plates by relative rotation of said rotor and said statorabout the common axis..

2. A variable condenser having a rotor and a stator each comprising apla-te Wound in a spiral about the mutual common axis, the two platesada ted to intermesh with and being spaced rom each other, means toadjust one of said plates relative to the other in the direction of thecommon axis, and means to move one et the said Y plates angularly yaboutthe common axis of the turns of one plate with regard to the' adjacentturns of the other pla-te, and means to hold said plates againstvariation of said spacing.

4. In a variable condenser. a stator plate in the form of a rigidspiral, a rotor plate infthe form of a rigid spiral, said plates lhaving the saine uniform spacing along .a radius and adapted tointerinesh with each other, the outer ends of one of said plates havinga greater spacing from the adjacentturn of the other plate than the saiduniform spacing, and means to vary the length of the outer end portionof said first plate having said greater spacing.

ln a variable condenser. a vstator comprising a met-al plate in thetorni of a spiral having a uniform angle of intersection with aradius, arotor plate similarly formed and adapted to intermesh with the stator,so that the turns of the respective platesare uniformly spaced along aradius, a hollow shalt for the rotor with keying means permitting therotor to slide in the direction of its axis and securing it to the shaftto rotate therewith, a threaded .pin extending through the hollow shaftand secured to the rotor, a .nut engaging the pin to move the rotor inthe direction of its axis into and out of intermeshed relation with thestator plate to adjust the eective capacity, and means to turn the rotorshaft to adjust the width of the air gap between the plates to vary theeffective capacity.

Signed by me at Baltimore, Maryland, this 2nd day of February, 1925.

' ARTHUR RUSSELL.

